Carpal tunnel syndrome (CTS) is one of the most common causes of work-related disability in the US. The most common pathological finding in CTS is non-inflammatory fibrosis and thickening of the subsynovial connective tissue (SSCT), but whether this fibrosis is a cause of or merely an associated finding in CTS is unknown. This study will address this important issue by investigating the relationship of the SSCT to carpal tunnel syndrome in an animal model. The model that we have selected is based on the concept of proliferative therapy, or prolotherapy, a treatment that induces cellular proliferation and fibrosis, and, thus, healing, by injection of a proliferant solution. We have preliminary evidence that a single injection of 10% dextrose into the rabbit carpal tunnel can induce a non-inflammatory proliferative response in the SSCT very similar to that seen in patients with CTS, culminating eventually in the development of demyelination of the median nerve. In this competitive renewal, we propose to validate this rabbit model, specifically to test the hypothesis that damage to the SSCT in the model results in a progression of fibrosis, altered material properties and increased pressure in the carpal tunnel leading to median neuropathy, similar to that seen in CTS patients. To test this hypothesis, we propose four specific aims: to compare the changes in material properties and carpal tunnel pressure in our animal model with those seen in CTS patients;to compare the histology, immunohistochemistry and ultrastructure of the SSCT in our animal model and CTS patients;to compare the evolution of electrodiagnostic changes in the median nerve (and nerve histology in animals only) in our animal model and CTS patients;and to compare the effectiveness of higher, lower, and sequential dextrose injections on the evolution of SSCT fibrosis and median neuropathy in our rabbit model. If these aims are achieved, and our hypothesis is supported, then for the first time we will have a validated animal model which mimics the clinical evolution of CTS. This model would allow us to study interventions directed at halting or reversing the evolution of SSCT fibrosis, and thereby the development of CTS. The model would also allow us to study the pathogenesis of CTS in more detail.